Industrial useful field
This invention relates to a catch-in prevention mechanism for a rotary valve which carries out a constant volume discharge of granules such as plastic pellets etc.
In a principal structure of such a rotary valve, a rotor 3 having plural blades 4 rotates in a rotor case 5 in a direction R so as to discharge pellet etc., which is thrown in from an upper side granule throw-in port 1, to a lower side discharge port 6 as illustrated by FIG. 7.
A problem by which the rotary valve is confronted, is how to prevent a phenomenon that granules are caught in between an outer peripheral edge of the blade 4 and an inside wall of the rotor case 5 so as to be deformed and collapsed in the vicinity of a front edge B in rotor rotation direction of the granule throw-in port 1, i.e. how to prevent a granule catch-in phenomenon.
As a device for preventing the granule catch-in phenomenon a device shown in FIG. 8 Japanese Published Utility Model Application ,Jikkaisyo 60-137945) or a device shown in FIG.9 Japanese Published Patent Application , Tokkaisyo 61-145039) has been developed.
In the device of FIG. 8, a shielding part 7 is provided at a central portion in a widthwise direction of the throw-in port 1, and a scratch-off edge 9 of an inclining wall 8 and an auxiliary throw-in groove 10 are formed into a backward-facing V-shape. That is, a central hollow portion (S of FIG. 5) is formed on a pellet in a rotor pocket by controlling a central portion of opening part by the shielding portion 7, so that the caught-in phenomenon is prevented. Further, a charging efficiency is also improved by supplementing the pallet to the central hollow portion of pellet with the auxiliary throw-in groove 10.
The device of FIG. 9 has an approximately similar structure to that of FIG. 8, in principle. In this device, the shielding part 7 is provided at the central portion in the widthwise direction of the throw-in port 1, and the auxiliary throw-in groove 10 is formed into the backward-facing V-shape.
In the above-mentioned structures, however, the following disadvantages arise. The shielding part 7 provided at the central portion in the widthwise direction of the throw-in port 1 connects up to a rear edge la of the throw-in port 1 to completely separate the opening part to both left and right sides, so that long tape-form froths produced in a pneumatic transportation pipe are caught at the shielding part 7.
Further, since the auxiliary throw-in groove 10 is formed into the V-shape opening to the rear side of the rotation direction, leaking air is concentrated at a front end F of the V-shaped auxiliary throw-in groove 10 and the leaking air is blown up from this place, when a pressure caused by a pneumatic transportation, etc., is applied on a lower part of the rotary valve. The pellet is stirred up by the blowing-up air at the F portion, so that the catch-in trouble prevention function does not work completely.
In FIG. 8 and FIG. 9, the catch-in state between the scratch-off edge 9 and the blade 4 might occur because of a small angle made by the scratch-off edge 9 and the blade 4. SUMMARY OF THE INVENTION
An object of this invention is to provide a catch-in prevention mechanism for preventing catch-in of granules by installing a V-shape scratch-off edge and a central shielding part on a throw-in port; characterized in that a caught-in tape-form froth etc. is remedies and local blowing up of leaking air from a discharge port side is prevented so that the catch-in prevention function can be further enhanced.
An object of this invention as set forth in claim 2 is to prevent a catch-in phenomenon from arising between a blade and a scratch-off edge.
In order to accomplish the above object, a rotor having plural blades is supported in a rotor case in such a manner as to be rotatably driven around a horizontal shaft, a blade is formed to have a V-shape or a curved shape opening to a front side in the rotation direction of the blade, inclining walls which have scratch-off edges opening into a V-shape toward a rear side as viewed from above and a shielding part which protrudes into a reverse-V-shape toward the rear side from a front central part of the inclining wall, are installed on a granule throw-in port provided on an upper part of the rotor case, a rear tip end of the shielding part is spaced from a rear edge of the throw-in port with a clearance left between them, a concave portion having a depth through which plural granules can pass is formed on a bottom surface of the shielding part, and air-vent grooves, which extend from a front side of rotation direction to a rear side of rotation direction relatively to the blade at time of passing the front end of the scratch-off edge, are formed on bottom surfaces of the inclining walls.
Further, a rotor having plural blades is supported in a rotor case in such a manner as to be rotatably driven around a horizontal shaft, a blade is formed to have a V-shape or a curved shape opening to a front side in the rotation direction of the blade, inclining walls which have scratch-off edges opening into a V-shape toward a rear side as viewed from above are installed on a granule throw-in port provided on an upper part of the rotor case, and an angle made by the rotor blade and the scratch-off edge is so preset as to be over 45.degree. inclusive.
The tip end of the shielding part is spaced from the rear edge of the throw-in port by a distance, so that there is no chance for a long froth to be caught in and accumulated around the shielding part even if the long froth is mingled in the thrown-in pellet.
A small space (non-charged section) is formed at the central portion of widthwise direction of rotor in the pellet supplied to the pocket between the blades, by means of an action of the shielding part. The pellet scratched off by the scratch-off edge is gathered to the central side as the blades move, and is positively put in the space of the pocket. An angle made by the blade and the scratch-off edge is taken large such as above 45.degree. inclusive, so that there is no chance for the pellet to be caught at the scratch-off edge
A concave portion having a size corresponding to two or three pellets is formed on the bottom surface of the shielding part, so that the catch-in phenomenon does not arise at the edge of the shielding part.
When a pressure at a discharge side is kept high due to a high-pressure gas type pneumatic transportation system, the leaking air passes from the air-vent grooves through the concave portion to the throw-in port. Accordingly, the leaking air does not concentrate at and blow up from the front edge of the scratch-off edge.